1. Field of the Invention
The present invention relates to pressure responsive flow control apparatus particularly adapted for use in combination with emergency breathing apparatus which includes a hood adapted to fit about a wearer's head for receiving the breathing gas.
2. DESCRIPTION OF THE PRIOR ART
Emergency breathing systems employing a hood to fit about a wearer's head are already available. One such system utilizes a hood made of transparent plastic material that fits snugly about the wearer's neck such that it also serves as an exhalation valve, venting the hood to maintain a suitable controlled pressure. Characteristically, such a breathing system includes regulating means to maintain hood pressure and also the rate of breathing gas flow substantially constant despite diminishing source pressure.
The source of pressure in such a system is usually a compressed air bottle adapted to provide air for a relatively short period of time, long enough for example to enable the wearer to escape from a smoke-filled building. However, the cumulative effect of the carbon dioxide in the exhalation collecting in the hood has an adverse effect on the wearer and a need exists for flushing out or otherwise ridding the hood of undesirably high concentrations of such carbon dioxide.